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[英]How can I check if an array of strings is empty in MongoDB with java?
[英]How to check for an empty Optional array of strings in Java?
如何检查 Java 中的空字符串可选数组?
如果是空的,我想返回一条消息。
@PostMapping("/users")
@ResponseBody
public String saveUsers(@RequestParam Optional<String>[] paramArray) {
System.out.println("param " + paramArray);
String msg = "";
int i = 0;
if (paramArray is empty) {
msg = "paramArray is empty";
} else {
for (Optional<String> paramArrayItem : paramArray) {
msg += "param[" + i + "]" + paramArrayItem + "\n";
i++;
}
}
return msg;
}
Optional<String>[]
是Optional<String>
元素的数组。
您宁愿拥有可选的字符串数组,因此您需要将paramArray
类型更改为Optional<String[]>
。
@PostMapping("/users")
@ResponseBody
public String saveUsers(@RequestParam Optional<String[]> paramArray) {
System.out.println("param " + paramArray);
String msg = "";
int i = 0;
if (paramArray.isEmpty()) {
msg = "paramArray is empty";
} else {
for (String paramArrayItem : paramArray.get()) {
msg += "param[" + i + "]" + paramArrayItem + "\n";
i++;
}
}
return msg;
}
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